This invention relates to sequential control devices for efficiently controlling a process or manufacturing line of a plant of any kind.
In controlling the route or operation of a manufacturing line or a transferring conveyor line which employs a plurality of electric actuating devices such as electric motors or an equal number of electric actuating devices, wherein the operation, stop and resting of each motor is to be properly controlled or operated in a complicated sequence, which uses contact relays, non-contact relays or micro-computors, heretofore the wiring between relays had to be installed by hand on the site, and the relays had to be attached to the machines and operated after the wiring had been carefully checked.
The following are some of the problems which afflict such a prior art arrangement:
(1) Drawings or sequence design schemes become complicated and greatly increase in number thereby consuming a great amount of time and labor.
(2) Installation of prior control circuits cannot be achieved by the appointed date of delivery. Many difficulties arise after installation since the sequence design and wiring cannot be thoroughly checked due to the complexity and limited time period for installation.
(3) Furthermore, since a great number of relays and complicated wiring are employed in the sequence, maintenance and remodelling of the sequence becomes extremely difficult, and the control itself becomes large in size. A professional engineer who is well versed in the sequence control is required for daily maintenance, in addition to making repairs.
The following conditions must be satisfied to resolve the above mentioned disadvantages of conventional sequence design and the sequence controls which use such design:
(1) All necessary electrical connections to control one electric actuating device should be assembled and incorporated into one unit.
(2) Each unit must function to control the transmission of separate regulating signals both to the immediately preceding unit and to the immediately succeeding unit.
(3) Each unit must be standardized and equalized so that one unit is interchangable with another unit.
(4) A connector must be used in connecting two adjacent units so that wiring at the installation site is minimized.
(5) An indication of the kind of operation in progress, such as normal operation, the occurrence of the trouble and so on, should be effected within each unit, so that even a layman can judge whether an electric actuating device is operating normally or is out of order.
(6) In the drawing of the sequence, the control circuit within the electric actuating device, such as a motor, must be created as a separate unit so that details of the circuit can be omitted.
It is an object of the present invention to provide a sequential control device which comprises a master control unit and a plurality of drive units applicable to the control of a plurality of electric motors in series in production or manufacturing lines which satisfies the above mentioned operational conditions.
It is another object of the present invention to provide a sequential control device which comprises a master control unit, drive units and cross units applicable to the control of a complicated production or manufacturing line which comprises at least two production lines in which a plurality of electric actuating devices are arranged in series in each line. Due to the employment of the cross units in the desired positions of the entire device, several process routes can be created, whereby the entire production line can achieve flexibility in the processing or manufacturing of products.
A further object is to provide prewired control, drive, and transfer units that can be mass-produced for use in plant lines of production by simply connecting any required number to one another and to the electrically controlled drives of the lines, to form a sequential device for the motors of such lines.